1. Technical Field
The present invention relates to a time difference information supply system for supplying time difference information of communication base stations, a terminal unit, a control method for a terminal unit, a control program for a terminal unit, and a recording medium for computer-reading on which a control program for a terminal unit is recorded.
2. Related Art
Currently, a positioning system for determining a location of mobile stations based on signals coming from a plurality of base stations in a so-called CDMA (Code Division Multiple Access) type digital mobile communication system has been proposed, for example (e.g., JP-A-7-181242).
According to this positioning system, time required for positioning signals to reach a mobile station from the respective base stations (hereinafter referred to as propagation time) is obtained, for example, when time differences between the respective time of the base stations and reference time are known. Then, the location of the mobile station is determined based on the propagation time thus obtained.
However, when each of the base stations requires one time difference measuring device, for example, for measuring the time differences of each base stations, it is necessary to provide the time difference measuring device for each of a great number of base stations existing throughout the country. This requires sufficient places for time difference measurement and notification, and therefore imposes serious financial burden.